Russia says it has opened a criminal investigation into the beating by riot police of an opposition protester in the capital on Sunday, the eve of Vladimir Putin's presidential inauguration.

Investigations Committee spokesman Vladimir Markin said Friday the probe will try to establish who shot the video, which was posted on the Internet, and identify police officers who used violence against the unidentified woman protester.

Moscow's NTV television aired the amateur video, which showed riot police dragging a young woman along the street and one officer kicking her in the stomach.

Moscow police detained hundreds of protesters during Sunday's rally, one of an ongoing series of demonstrations against Russia's elections and Putin's return to the presidency.

Mr. Putin was elected to a third presidential term in March with 64 percent of the vote. He served as president from 2000 to 2008, but term limits prevented him from running for a third consecutive term. He then became prime minister under former president Dmitry Medvedev.

A constitutional amendment has extended the president's time in office to two consecutive six-year terms, meaning Putin could stay in power until 2024, an outlook many Russians find unsettling.